Sustainable architectural lightweight aggregates from sewage sludge ash: synergistic enhancement by alkali activator temperature and PVA fibers

Le résumé fourni par la source

The large-scale production of sewage sludge ash (SSA) from incineration poses environmental challenges, yet cold-bonded technology offers a low-energy route to produce lightweight aggregates (LWA). However, insufficient strength limits its application. This study demonstrates that increasing the alkali activator temperature from 20 °C to 40 °C increases bulk density by 32%, reduces water absorption by up to 17%, and improves 28‑day crushing strength by 194% under standard curing. Sealed curing further enhances strength by 5.7% over standard curing at 40 °C. Incorporating 0.3 wt% polyvinyl alcohol (PVA) fibers under sealed curing yields the highest bulk density of 895 kg/m3, lowest water absorption of 21.8%, and highest crushing strength of 6.9 MPa, representing a 283% increase over the baseline such as 20 °C activator and standard curing. Microstructural analyses including SEM, XRD, MIP reveal that the elevated activator temperature accelerates geopolymerization, forming a denser gel matrix, while PVA fibers bridge microcracks and enhance matrix continuity. Sealed curing and fiber addition also increase surface roughness, which is beneficial for interfacial bonding in concrete. These findings provide an energy‑efficient strategy for producing high‑performance cold‑bonded SSA‑LWA and promoting sustainable reuse of incineration residues.

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